The use of powder and essential oil of Cymbopogon citratus against mould deterioration and aflatoxin contamination of 'egusi' melon seeds

Experiments were carried out to determine the potential of using the powder and essential oil from dried ground leaves of Cymbopogon citratus (lemon grass) to control storage deterioration and aflatoxin contamination of melon seeds. Four mould species: Aspergillus flavus, A. niger, A. tamarii and Penicillium citrinum were inoculated in the form of conidia suspension (approx. 10(6) conidia per ml) unto shelled melon seeds. The powdered dry leaves and essential oil from lemon grass were mixed with the inoculated seeds at levels ranging from 1 - 10 g/100 g seeds and 0.1 to 1.0 ml/100 g seeds respectively. The ground leaves significantly reduced the extent of deterioration in melon seeds inoculated with different fungi compared to the untreated inoculated seeds. The essential oil at 0.1 and 0.25 ml/100 g seeds and ground leaves at 10 g/100 g seeds significantly reduced deterioration and aflatoxin production in shelled melon seeds inoculated with toxigenic A. flavus. At higher dosages (0.5 and 1.0 ml/100 g seeds), the essential oil completely prevented aflatoxin production. After 6 months in farmers' stores, unshelled melon seeds treated with 0.5 ml/ 100 g seeds of essential oil and 10 g/100 g seeds of powdered leaves of C citratus had significantly lower proportion of visibly diseased seeds and Aspergillus spp. infestation levels and significantly higher seed germination compared to the untreated seeds. The oil content, free fatty acid and peroxide values in seeds protected with essential oil after 6 months did not significantly differ from the values in seeds before storage. The efficacy of the essential oil in preserving the quality of melon seeds in stores was statistically at par with that of fungicide (iprodione) treatment.